Method and apparatus for control of misting



Dec. 5, 1961 R. w. JONES EEAL METHOD AND APPARATUS FOR CONTROL OFMISTING Filed July 29. 1959 BLANKET CV LINDER United States PatentCfitice sawed villi} 1 11i 3,011,435 METHOD AND APPARATUS FOR CONTROL OFMISTENG Rexford W. Jones, Robert B. Reif, and Lewis E. Wallrup,Columbus, Ohio, assignors, by mesne assignments, to Cutler-Hammer, Inc.Milwaukee, Wis, a corporation of Delaware Filed July 29, 1959, Ser. No.830,353 7 Claims. (Cl. 101-850) This invention relates generally tomethods and apparatus for the electrostatic control of particles.

While not limited thereto, the invention relates particularly to methodsand apparatus for electrostatically controlling ink mist produced in inkdistribution systems or ink trains of high speed printing presses.

So-called ink mist or ink fog in press rooms has long been a seriousproblem in the printing industry and is becoming more aggravated asprinting press speeds increase. The presence of ink mist affects thehealth and morale of press room personnel, creates hazardous conditions,wastes ink, contaminates the finished printed product, and necessitatescostly periodic cleanups and elaborate and expensive control measures.Ink mist or fog, which is to be distinguished from so-called ink slingor ink fly, i.e., ink particles occasionally thrown off of individualinked rollers in an ink train by the action of centrifugal force, isformed when the ink film between a roller couple splits at the exit sideof the roller nip. As the ink film splits, filaments of ink are formedwhich rupture almost as quickly as they are formed into extremely smallink particles which eventually find their way into the atmosphere in theform of mist. Prior attempts to eliminate, suppress or otherwise controlink mist, as by filter or blower systems, use of special types of ink oreven certain methods of electrostatic precipitation, have not provenentirely satisfactory from the standpoint of efliciency or cost.

.Accordingly, it is an object of this invention to provide improvedmethods and apparatus for controlling mist generated in apparatus, suchas printing presses or the like, which employ roller couples to conveyliquid material from one roller to another.

Another object is to provide improved methods and apparatus of theaforesaid character which return the mist to its source as distinguishedfrom methods and apparatus which attempt to remedy the mist conditionafter the mist particles have escaped from the nip area.

Still another object is to provide improved methods and apparatus of theaforesaid character which employ electrical principles to drive liquidparticles back onto the rollers from whence they came before they canescape from the nip area.

A more specific object is to provide improved methods and apparatus ofthe aforesaid character wherein electrical effects accompanying a coronadischarge are employed to electrically charge liquid mist particles asthey are formed and to create an electrostatic field which acts to forcesaid charged mist particles back onto said rollers.

An even more specific object is to provide improved apparatus wherebymist particles generated at the exit side of the nip of a roller coupleare forced back onto said roller as the result of electrical effectsattending a corona discharge when a highly charged conductive member isdisposed adjacent the nip on the exit side thereof, said corona effectbeing accompanied by an electrostatic field which exists between saidconductive member and said rollers and by electrical charging of saidmist particles.

Still another object is to provide apparatus of the aforesaid characterwhich is practical, efficient, relatively economical to manufacture andemploy, fundamental in concept, employs a minimum number of components,and

stream around other rollers.

which lends itself readily to a wide variety of applications.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of theinvention, it being understood that the embodiments illustrated aresusceptible to modification with respect to details thereof withoutdeparting from the scope of the appended claims.

FIGURE 1 is a schematic showing the ink distribution system or ink trainof a typical printing press with which the invention is employed;

FIG. 2 is an enlarged view of two rollers, or a roller couple, of theink train shown in FIG. 1 showing the disposition of a corona wire withrespect thereto; and

FIG. 3 is a diagrammatic showing of the electrical circuitry foreffecting energization of the corona wire shown in FIG. 2 fromalternating current or either polarity of direct current.

FIGURE 1 scematically depicts part of the ink distribution system or inktrain of a typical modern high speed printing press with which theinvention is employed to particular advantage. The numeral 10 designatesan ink fountain from which ink is picked up by the fountain roller 11and subsequently transferred to ten other rollers 12, 13, 14, 15, 16,17, 18, 19, 20 and 21, to thin it and evenly distribute it before it isfinally transferred to the plate cylinder 22 which is adjacent theblanket cylinder 23. The several rollers and cylinders may be assumed tobe suitably supported by a framework (not shown) and are driven in thedirection of the arrows by suitable driving means (not shown) when theprinting press is in operation. In a typical high speed newspaper pressthe peripheral velocity of the inking rollers might range, for example,from 1,700 feet per minute to 2,120 feet per minute. At such speedsanywhere from 40,000 to 70,000 printed copies can be produced. In theink train, the inking rollers 11, 12, 14 and 13 may be assumed to bemade of steel whereas the rollers 13, 15, 16, 17, 19, 20 and 21 are madeof steel covered with a layer of resilient material. Thus, for example,in one roller couple shown in FIGS. 1, 2 and 3 the roller 14 may beassumed to be of steel and the roller 17 with which it is contiguous maybe assumed to be of steel covered with a layer 17a of Buna-N rubber orlike material on the order of one-half inch thick. The area of contactbetween two rollers, such as rollers 14 and 17 in FIGS. 1, 2 and 3, iscalled the nip and the exit side of the nip, which is so labeled in FIG.2, is the location whereat ink mist is initially produced. Although itis to be understood that the ink mist is generated at the eixt side ofthe nip of each roller couple, the hips of some couples are so situatedthat the mist generated thereat is not able to escape from the immediatearea. Two such areas, for example, are designated by the numerals 50 and51 in FIG. 1. The locations of the major sources of mist formation inthe particular ink train illustrated are designated as position 24, 25,26, 27, 28, 29 and 29a in FIG. 1 but in other apparatus these locationsmight differ.

Mist is formed when the ink film on two rotating contiguous rollers,such as rollers 1d in FIGS. 1. 2 and 3, splits at the exit side of thenip. Filaments of ink are formed as the film splits and the filamentsrupture almost as quickly as they are formed. Rupture of the filamentsresults in the formation of extremely small particles of ink whichcomprise the mist. The mist particles are not expelled into theatmosphere at the nip exit where they are formed but tend to follow theperiphery of the rollers in an air stream therearound until they areforced from this path by the air turbulence resulting from the airHowever, some particles leave the periphery of the rollers on atangential line about 45 degrees from the nip from whence theyoriginate.

Generally speaking, the nature of the ink filaments and the amount ofmist produced depends on ink film thickness, the rheological propertiesof the particular ink employed, the peripheral velocity of the rollers,and roller interference. Thus, for example, an ink film thickness offrom 0.0002 to 0.0004 inch on the rollers might occur when newspapersare being printed, whereas a thicker film and more viscous ink would beneeded for printing cardboard. Peripheral velocities may vary, asherein'oefore discussed, depending on press speeds.

In accordance with the, present invention, control or suppression of theink mist is effected by electrostatically forcing the ink particles backonto the rollers from whence they originate. To accomplish this,electrically conductive members, such as wires, are disposed close tothe exit side of the roller nips in parallel relationship to therollers. The rollers forming the couple are maintained at groundpotential and the conductive members are raised to a high electricalpotential from a suitable source of electrical power so that a coronadischarge occurs therealong and so that an electrical field isestablished between the conductive member and the rollers. The coronadischarge is attended by intense ionization of the air surrounding theconductive member and the electrical charge is transferred from the airto ink mist particles in the nip area. The ink particles are repulsedfrom the conductive member and then forced back onto the rollers as aresult of the force exerted on the charged ink particles by theelectrical fields which exist between the conductive members and therollers adjacent thereto.

tions are the major sources of mist production, as hereinbeforeexplained. However, to facilitate understanding of the invention, onlythe constructionand operation of the conductive member 25a, shown inFIGS. 2 and 3, located at position 25, shown in FIG. 1, in associationwith the rollers 14 and 17 will hereinafter be described.

Referring now to FIGS. 2 and 3, it is seen that a conductive member suchas a wire 25a is arranged parallel to and in close proximity to the exitside of the nip between rollers 14 and 17. In practice, the wire 25a canbe mechanically mounted on a suitable portion of the ink train frame(not shown) provided it is electrically insulated therefrom. However,other means (not shown) for sup- .porting the wire'25a in properposition may be employed.

In producing corona emission, higher voltages are required as wirediameter increases, therefore, it is preferred to employ a wire of smalldiameter to reduce power requirements, but of sufiicient mechanicalstrength to be drawn taut. Steel wires having a diameter of from 0.004to 0.064 inch were found satisfactory when located as shown andenergized to the degree hereinafter more particularly described. Inlocating the wire 25a with respect to the adjacent rollers, it isdesirable that it be as close thereto as is consistent with practicalconsiderations, but not in electrical contact therewith, in order tohave maximum electrical field strength between the wire 25a and therollers 14 and 17, which rollers serve as grounded electrodes, as willhereinafter appear. Preferably, field strength between wire 25a and eachroller 14 and 17 should be equal, and since, as hereinbefore described,roller 14 is steel and roller 17 is electrically insulated to someextent by a rubber cover 17a, it is necessary to place wire 25a closerto roller 17 than to roller 14 to obtain equalized field strength.Assuming, for example, wires of the diameter hereinbefore described andenergization thereof to the degree hereinafter described, a distance ofthree-fourths of an inch between wire 25a and the surface of roller 14and a distance of three-eighths of an inch between wire 25a and thesurface of roller 17 are found to be quite satisfactory from thestandpoint of effectiveness of mist control, current requirements, andpracticality.

FIG. 3 shows schematically the electrical circuitry employed to effectenergization of wire 25a. The voltage applied to wire 25a must besufficiently high to produce corona emission therefrom capable ofcharging all ink mist particles in the vicinity and to create an electcal field strong enough to drive all of the charged ink ticles back ontothe rollers 14 and The voltage required to effect this is related towire diameter and its distance from the rollers. Assuming wire diametershereinbefore described and locationhereinbefore described, a voltage ofthe order of 15,000 to 20,000 volts with a current of approximately 0.5milliampere per foot of wire produces satisfactory results. The powerapplied to Wire 25a may be supplied froma direct current source ofeither polarity or from'an alternating current source.

As FIG. 3 shows, wire 25a is adapted to be energized either byalternating current to provide an alternating corona and electrostaticfield or by direct current of either polarity to provide a positive ornegative corona and electrostatic field. Alternating or positive ornegative energization of wire 25a results in different corona effects,as will hereinafter appear.

FIG. 3 shows power supply lines L1 and L2 which may be assumed to beenergized from a suitable source of alternating current power supply(not shown). A step-up transformer 30 whose primarywinding 30a isconnected across lines L1 and L2, is provided to afford a source ofhighvoltage energization of the corona wire 25a. Corona Wire 25a is adaptedto be energized directly from the secondary winding 30b of transformer30 through switch 31 to provide an alternating corona, or from thesecondary winding 30b of transformer 30, through rectifier bridge 34,switch 36 and swith 31 to provide a direct current corona of eitherpolarity.

The end terminals 300 and 30d of secondary winding 3% of transformer 30are connected to the terminals 31b and 31a, respectively, of thenormally open double pole, double throw knife switch 31. Blade 310 ofswitch 31 is connected to corona wire 25a and blade 31a is connectedthrough conductor wire 40 to ground.

The end terminals 300 and 30d of secondary winding 30b of transformer 30are also connected to the input terminals 34a and 34b, respectively, ofthe rectifier bridge 34 which is of the well known type and comprisesfour dry rectifiers 34e, 341, 34g and 34h which are poled as shown inFIG. 3. The output terminals 340 and 34d of rectifier bridge 34, whichmay be assumed to be positively and negatively charged, respectively,are connected to the blades 36c and 36d, respectively, of the normallyopen double pole, double throw knife switch 36. minals 36a and 36b ofswitch 36 are connected to the terminals 36 and 36e, respectively, ofswitch 36 and the .to wire 25a could be connected in parallel with wire25a across the power supply, as will be apparent to those skilled in theart.

The invention operates as follows:

Assume that the printing press and. the ink train thereof are inoperation and that inkv is being conveyed from roller to roller at suchspeed that ink mist is being produced at the location 24, 25, 26, '27,28, .29 and 29a and v is escaping from the nip area, as hereinbeforedescribed. To simplify discussion, only the operative effect of wire 25aon the mist from rollers 14- and 17 will be hereinafter described indetail. Further assume the lines L1 and L2 tre energized,thattransformer 30 is energized therefrom, I

The terthat the switches 31 and 36 are both open and that wire 25a isnot energized.

Suppression or control of the mist produced by rollers 14 and 17 isaccomplished by effecting energization of wire 25a from either thealternating current source or the direct current source. When wire 25ais energized to a high electrical potential a corona discharge occurstherealong and, in addition, an electrical field is established betweenthe wire and the rollers 14 and '17 which act as grounded electrodes.

The corona discharge is visible as a bluish glow in a limited regionaround the emitting surface of the wire. The glow is caused by intenseionization which produces large numbers of ions of both polarities. Ionswith polarity opposite to that of the emitting surface of the wire areattracted to the emitting surface and are neutralized. Ions of the samepolarity as the emitting surface of the wire are repelled from theemitting surface and form a region of ions of a single polarity beyondthe glowing region. In their travel, many of the ions of single polaritybombard ink mist particles and the ions are captured by those particles.The charged ink mist particles are driven back onto the ink rolls by theforces exerted on the charged ink particles by the high voltageelectrical field which exists between wire 25a and the two rollers 14and 17, which rollers are at ground potential. In this manner, ink mistparticles are forced back onto the rollers 14 and 17 before they have anopportunity to escape from the nip area.

Upon deenergization of wire 25a the effect ceases and ink particlesagain escape from the nip area as hereinbefore described.

A direct current positive corona (the term positive referring to thepolarity of the ions in the corona) is produced by connecting wire 25ato the positive terminal 34c of rectifier bridge 34 and connecting thenegative ter' minal 34d of the bridge 34 to ground. This is accomplishedby closing switch 31 to the right-hand side so that blades 31c and 31dthereof make contact with contacts-31e and 31 thereof, respectively, andby closing switch 36 to the right-hand side so that blades 35c and 36dthereof make contact with contacts 36@ and 36 thereof, respectively.

A direct current negative corona (the term fnegative referring to thepolarity of the ions in the corona) is produced by connecting wire 25ato the negative terminal 34d of rectifier bridge 34 and connecting thepositive terminal 340 of bridge 34 to ground. This is accomplished byclosing switch 31 to the right-hand side so that blades 31c and 31dthereof make contact with contacts 3-12 and 31 thereof, respectively,and by closing switch 36 to the left-hand side so that blades 36c and36d thereof make contact with contacts 36a and 36b thereof,respectively. The difference between a positive and negative corona isthat positive discharge produces a continuous glow along wire 25awhereas negative discharge produces glow at discrete points along thewire. More important, however, a negative corona can be maintained athigher potential than a positive corona before arcing occurs andtherefore might be preferred because efficiency of ink particlerepulsion is dependent upon applied voltage.

Ink mist control can be effected by use of alternating current. Toaccomplish this, switch 36 is maintained open and the blades of knifeswitch 31 are moved in the lefthand direction to connect wire 25a to theend terminal 39d of secondary winding 30]) of transformer 30 and toconnect end terminal 30c to ground. The ink mist particles are forcedback onto the rollers 14 and 17 as hereinbefore described except thationization charges and field direction alterante at the frequency of theapplied voltage and the ei'ficiency of the A.C. system is somewhatlower.

The advantages of the hereinbefore described apparatus and method foreffecting ink mist control or suppression are manifold. In operation,assuming proper location of the corona wire and adequate energizationthereof, the

suppression of mist is almost percent efficient. Furthermore, as isapparent, the installation is relatively simple from an electrical andmechanical standpoint and employs a minimum of components. In practice,only one source of power would be required depending upon whether DC orAC. was found to be most suitable for individual needs. Since thepresent invention attacks the ink mist problem at its source and bypreventing escape of the mist from the nip area, rather than bycollection of mist already widely dispersed in the atmosphere, no wasteink collects or is precipitated which needs to be disposed of.

It will be apparent that the invention disclosed herein is applicable tocontrol mist comprised of material other than ink and generated byroller couples employed in machines other than printing presses.

We claim:

1. In a printing press, a roller couple for transferring liquid materialfrom one roller of the couple to the other, said couple when inoperation causing minute particles of said liquid material in the formof a mist to be produced in the atmosphere adjacent the exit side of thenip of said couple which mist if not suppressed contaminates thesurrounding atmosphere, and means for suppressing said mist to preventthe latter from contaminating the atmosphere comprising an electricalconductor disposed adjacent to said rollers of said couple and inrelatively short spaced relation to the exit side of said nip, and meansfor applying a high electrical potential between said conductor and atleast one roller of said couple to establish a corona discharge aboutsaid conductor and to establish an electrical field between saidconductor and said roller of said couple, said corona dischargeeffecting electrical charging of said particles and said electricalfield acting upon said charged particles to repel the latter back ontosaid roller.

2. In combination, a roller couple for transferring ink from one rollerof the couple to the other, said couple when in operation tending toproduce mist particles of said ink at the exit side of the nip of thecouple, and electrically conductive means disposed adjacent to saidcouple but spaced apart therefrom on the exit side of the nip, saidconductive means with said rollers electrically grounded beingenergizable to establish a corona discharge thereabout and to establishan electrical field between itself and said rollers, said coronadischarge effecting electrical charging of said ink mist particles andsaid electrical field acting upon said ink mist particles when thelatter are charged to force said particles back onto said rollers.

33. The combination according to claim 2, wherein said electricallyconductive means comprises a wire which is disposed parallel to the nipof said roller couple and is spaced with respect to each of said rollersin said couple so that electrical fields of substantially equal strengthexist between said wire and said roller.

4. The combination according to claim 3 together with a source ofvoltage and means for selectively connecting the same to said wire andground to subject said wire to a potential with respect to groundcreating a corona discharge thereabout, and the electrical field betweensaid wire and said rollers.

5. The combination according to claim 3 wherein said source of voltagewhen connected to said wire and ground subjects said wire to a DC.potential with respect to ground of a polarity creating a negativecorona. discharge about said wire.

6. In a printing press having an ink distribution system wherein ink istransferred from one roller to another, in combination, at least oneroller couple for transferring ink from one roller of the couple to theother when the couple is in operation, said couple tending to produceink particles at the exit side of the nip of the couple where the inkfilm. splits which particles normally leave the nip area in the form ofmist, at least one conductor disposed adjacent to and parallel to saidnip on the exit side thereof but spaced apart from said rollers, andmeans to electrically energize said conductor to produce a coronaefi'ect thereabout and an electrical acted upon by said electrical fieldare propelled back onto 5 said roller couple.

7. The method of suppressing ink mist produced by a high speed rollercouple wherein ink is being transsaid ink particles are present in saidelectrical field, said 15 charge being of such polanity with respect tosaid electrical field that said ink particles are forced back onto saidrollers.

References Cited in the file of this patent UNITED STATES PATENTS2,224,391 Huebner Dec. 10, 1940 2,691,343 Huebner Oct. 12, 19542,753,796 Wood et a1. July 12, 1956- 2,796,832 Pritchard June 25, 19572,869,461 Jarvis Jan. 30, 1959 I FOREIGN PATENTS 605,979 Great BritainAug. 4, 1948

